Fix a bad error case handling in read_cache_page_async()

Commit 6fe6900e introduced a nasty bug
in read_cache_page_async().

It added a "mark_page_accessed(page)" at the final return path in
read_cache_page_async().  But in error cases, 'page' holds the error
code, and you can't mark it accessed.

[ and Glauber de Oliveira Costa points out that we can use a return
  instead of adding more goto's ]
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/filemap.c

@@ -1784,7 +1784,7 @@ struct page *read_cache_page_async(struct address_space *mapping,
 retry:
 	page = __read_cache_page(mapping, index, filler, data);
 	if (IS_ERR(page))
-		goto out;
+		return page;
 	mark_page_accessed(page);
 	if (PageUptodate(page))
 		goto out;
@@ -1802,9 +1802,9 @@ struct page *read_cache_page_async(struct address_space *mapping,
 	err = filler(data, page);
 	if (err < 0) {
 		page_cache_release(page);
-		page = ERR_PTR(err);
+		return ERR_PTR(err);
 	}
- out:
+out:
 	mark_page_accessed(page);
 	return page;
 }